Roofs for contemporary buildings, particularly light industrial buildings having rectangular-shaped roofing, are typically formed from roof panel structures that are attached to main supporting beams. Completed roof panel structures may be 25 to 80 feet in length or even longer, and are often lifted to and placed on the main supporting beams by a crane or forklift. Once in place, the roof panel structures are attached, for example by nails, to the main supporting beams and adjacent roof panel structures. A plurality of the roof panel structures together form the roof.
An example of a prior art roof panel structure is generally designated as “A” in FIG. 1. The roof panel structure A includes a major horizontal beam, often called a purlin P. The purlin P in FIG. 1 is a solid structure, such as a glulam beam, a wooden beam, or the like. More recently, as described with reference to FIG. 2, below, the purlin P may include a steel truss, typically including wood or another material along a top edge that permits easy attachment of other components of the roof panel structure (e.g., by nailing).
Minor beams, called “subpurlins” (S in FIG. 2) extend orthogonally to the purlin P, and are often attached to the purlin P by right angle brackets B that extend from an end of the subpurlin. The subpurlins S may be made of any of the materials described above with respect to purlins P, but are typically lumber stiffeners of dimensional lumber, such as 2-by-6's, 2-by-4's, 3-by-4's, 3-by-6's, and so forth, six to ten feet in length.
Diaphragms D, such as wood structural panels (e.g., 4 by 8 feet, 4 by 10 feet, 8 by 8 feet, or 8 by 10 feet structural wood panels) are mounted over the subpurlins S and the purlin P, and are typically nailed to the subpurlins and the purlin for structural and shear support. In the embodiment shown in FIG. 1, the diaphragms D extend beyond both ends of the subpurlins S, and a front end of each of the diaphragms overlaps approximately one half of the thickness of the purlin P. The back ends of the diaphragms D rest on an adjacent purlin P in an adjacent roof panel structure A. Thus, diaphragms for two adjacent roof panel structures A are arranged end to end, with their adjoining surfaces centered over the purlin P.
Subpurlins S are located such that the edges of the diaphragm D overlap one half of the subpurlins that extend along the side edges of the diaphragm, and other, intermediate subpurlins (two shown in FIG. 1, but this number may be varied) are spaced between the two subpurlins on the side edges. Adjacent diaphragms D overlap the other half of the subpurlins S at the side edges.
A single roof panel structure A typically includes a purlin P and the subpurlins S and diaphragms D attached along only one side of the purlin. The number of diaphragms D and subpurlins S used in a roof panel structure A depends upon the spacing of the subpurlins, the width of the diaphragms, and the length of the roof panel structure. Typically, the diaphragms are 4 or 8 feet in width (although they may be less or more wide), and the subpurlins are spaced 24 inches on center (i.e., two edge subpurlins S and one intermediate for a 4 foot wide diaphragm, and two edge subpurlins and three intermediate subpurlins for a 8 foot wide diaphragm, and so forth). Completed roof panel structures A may be 25 to 80 feet in length, or even longer. When installed, these roof panel structures A extend orthogonally to main supporting beams (not shown, but known in the art) and are attached to the main supporting beams and adjacent roof panel structures by nailing or another appropriate attachment method. The distal edges of the subpurlins and diaphragms for one roof panel structure are attached the purlin of an adjacent roof panel structure so that a continuous roof surface is formed. An example method for assembling roof panel structures is described in U.S. Pat. No. 6,986,204, entitled “Method of Constructing Panelized Roof Structures.”
As stated above, traditionally, purlins P were formed of solid wood beams or glulam beams. More recently, however, purlins include a steel or other metal truss. Such a structure is lighter, less expensive, and easier to handle than a roof panel structure having a solid beam. An end view of an example of a roof panel structure having a truss purlin P with subpurlins S attached thereto is shown in FIG. 2.
In FIG. 2, the purlin P includes a truss T extending its length. A pair of angled brackets A are attached to a top surface of the truss T. A nailer board N is attached to the top of the angle brackets A.
To attach subpurlins S to the purlin P, the subpurlins are arranged so that the brackets B overhang the nailer board N. The brackets B are then nailed to the nailer board N. The ends of the subpurlins S are supported by the attachment of the brackets B to the nailer board N.
Typically, the nailer board N is a conventional lumber stiffener, such as a 2-by-6, 3×6 or 1¾″ lvl nailer. The nailer board N is preferably at least as wide as the combined angle brackets A, with minimal overlap beyond the angle brackets. Often, truss purlins P are provided to an installer that are of inconsistent width, requiring that the installer vary the width of the nailer boards used in an installation. This variation can slow construction. It can be understood that if a nailer board N as shown in FIG. 2 is a 2-by-6, then the dimension between the two subpurlins S is the standard for a 6 inch nominal board, or 5½ inches. In contrast, if a 2-by-8 is provided for the nailer board, then that 2-by-8, 3×8 etc., will separate the two subpurlins by 7¼ inches. This variation in dimension requires that an installer cut the lengths of the subpurlins S to create a consistent spacing between purlins P. The custom fitting of the subpurlins S to the width of the nailer boards N is time consuming and expensive.